Magnetic navigation system

ABSTRACT

A system for magnetically navigating a medical device in an operating region within the body of a patient. The system includes a magnet having a front field projecting from the front of the magnet sufficient to project a magnetic field into the operating region in the patient. The magnet is mounted for movement between a navigation position in which the magnet is located adjacent to the patient with the front of the magnetic generally facing the operating region, and an imaging position in which the magnet is spaced from the patient and the front generally faces away from the operating region.

CROSS REFERENCE TO RELATED APPLICATION

This is a Continuation-in-Part of U.S. patent application Ser. No.10/056,227, filed Jan. 23, 2002, for Rotating and Pivoting Magnet forMagnetic Navigation, incorporated herein by reference.

BACKGROUND OF THE INVENTION

This system relates to magnetic navigation of medical devices in thebody, and in particular to a system for applying a magnetic field ofselected direction to an operating region in a subject's body to orienta magnetically responsive medical device.

Magnetic navigation of medical devices has significantly improved toability of medical professionals to control medical devices in the body.Early magnetic navigation techniques involved the use of superconductingmagnets. While these techniques were, and remain, highly effective,advances in permanent magnetic materials and in the design of permanentmagnets, have made it possible to use permanent magnets for magneticnavigation. While the magnetic fields created by superconducting magnetscan be readily changing the currents in the superconductingelectromagnetic coils, in order to change the magnetic field created bypermanent magnets for navigation, it is generally necessary to changethe position and/or orientation of the permanent. In order to accuratelycontrol the magnetic field applied by permanent magnets, it is necessaryto accurately control the position and/or orientation of the permanentmagnet.

SUMMARY OF THE INVENTION

The present invention relates to a magnetic navigation system, and inparticular to a system including magnet units comprising a permanentmagnet, and a support for controlling the position and orientation of apermanent magnet. The system is adapted for magnetically navigating amedical device in an operating region within the body of a patient.Generally, the system comprises a magnet having a front field projectingfrom the front of the magnet sufficient to project a magnetic field intothe operating region in the patient. The magnet is mounted for movementbetween a navigation position in which the magnet is located adjacent tothe patient with the front of the magnetic generally facing theoperating region, and an imaging position in which the magnet is spacedfrom the patient and the front generally faces away from the operatingregion.

According to another aspect of the invention the system includes amagnet system comprising: a magnet and a support for mounting the magnetand changing the position and orientation of the magnet to change thedirection of magnetic field applied to the operating region. The supportis preferably capable of pivoting the magnet about a first axis thatrotates about a second axis perpendicular to the first axis, andtranslating the magnet, preferably parallel to the second axis.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a magnetic surgery suite incorporatingmagnet assemblies in accordance with the principles of this invention;

FIG. 1A is a top plan view of the magnetic surgery suite;

FIG. 2 is an exploded front perspective view of one of the magnetassemblies (the other magnet assembly being a mirror image thereof),with the cover removed to show details of construction;

FIG. 3 is a front perspective view of the magnet assembly, with thecover removed;

FIG. 4 is a front perspective view of the magnet assembly, showing thelower cover;

FIG. 5 is a front perspective view of the magnet assembly, showing theupper cover;

FIG. 6 is a rear perspective view of the magnet assembly;

FIG. 7 is a front elevation view of the magnet assembly;

FIG. 8 is a further exploded front perspective view of the positionersystem of the magnet assembly

FIG. 9 is a front elevation view of the positioner system of the magnetassembly;

FIG. 10 is a left side elevation view of the positioner system of themagnet assembly

FIG. 11 is a right side elevation view of the positioner system of themagnet assembly;

FIG. 12 is a rear elevation view of the positioner system;

FIG. 13 is a top plan view of the positioner system;

FIG. 14 is a bottom plan view of the positioner system;

FIG. 15 is a front elevation view of the phi drive mechanism of themagnet assembly;

FIG. 16 is a top plan view of the phi drive mechanism;

FIG. 17 is a left side elevation view of the phi drive mechanism;

FIG. 18 is a right side elevation view of the phi drive mechanism;

FIG. 19 is a front elevation view of the front plate of the phi drivemechanism;

FIG. 20 is a left side elevation view of the front plate of the phidrive mechanism;

FIG. 21 is a right side elevation view of the front plate of the phidrive mechanism;

FIG. 22 is a horizontal transverse view of the front plate of the phidrive mechanism, taken along the plane of line 22—22 in FIG. 19;

FIG. 23 is an exploded perspective view of the phi drive mechanism;

FIG. 24 is a front elevation view of the theta drive mechanism of themagnet assembly;

FIG. 25 is a top plan view of the theta drive mechanism;

FIG. 26 is a left side elevation view of the theta drive mechanism;

FIG. 27 is a bottom plan view of the theta drive mechanism;

FIG. 28 is a front perspective view of the theta drive mechanism;

FIG. 29 is a front elevation view of theta drive motor;

FIG. 30 is a top plan view of the theta drive motor;

FIG. 31 is a bottom plan view of the theta drive motor;

FIG. 32 is a left side elevation view of the theta motor;

FIG. 33 is an exploded front perspective view of the theta motor;

FIG. 33 is an a top plan view of the z drive mechanism

FIG. 34 is an front elevation view of the z drive mechanism;

FIG. 35 is a left side elevation view of the z drive mechanism;

FIG. 36 is a right side elevation view of the z drive mechanism;

FIG. 37 is bottom plan elevation of the z drive mechanism;

FIG. 38 is an exploded perspective view of the z drive mechanism

FIG. 39 is a perspective view of the pedestal;

FIG. 40 is an exploded front perspective view of the pedestal showingthe pivot assembly, the drive system assembly, and the locking system;

FIG. 41 is an exploded front perspective view of the pedestal with thepivot assembly, the drive system assembly, and the locking systemassembly removed;

FIG. 42 is a bottom plan view of the pedestal;

FIG. 43 is a longitudinal cross sectional view of the pedestal takenalong the plane of line 43—43 in FIG. 42;

FIG. 44 is a side elevation view of the pedestal;

FIG. 45 is an exploded perspective view of the pivot assembly forpivotally mounting the pedestal;

FIG. 46 is a perspective view of the drive mechanism;

FIG. 47 is a perspective view of the drive assembly.

FIG. 48 is a side elevation view of the magnet.

FIG. 49 is a front elevation view of the magnet.

Corresponding reference numerals indicate corresponding parts throughoutthe several views of the drawings.

DETAILED DESCRIPTION OF THE INVENTION

A magnetic surgery suite incorporating magnet units in accordance withthe principles of this invention is indicated generally as 20 in FIG. 1.As shown in FIG. 1, the suite 20 comprises an operating room 22 and acontrol room 24. The control room 24 is preferably adjacent to theoperating room 22, and has a window 26 from which the procedure takingplace in the operating room 22 can be viewed. However, the control room24 does not have to be adjacent to the operating room 22, and insteadcould be located remotely from the operating room, for example on adifferent floor, or in a different building, or even in a differentcity.

The operating room 22 includes a patient support, such as a patient bed26, and a pair of magnet units 28 and 30, disposed on opposite sides ofthe patient bed to project a magnetic field into the operating region ina patient on the patient bed. The operating room also includes animaging system 32, comprising a C-arm mounting at least one x-ray source34 and at least one x-ray receiver 36, such as an amorphous siliconimaging plate. Cabinets 38 and 40 are provided for computer controllersand other electronics for operating the magnet units 28 and 30 and theimaging system 32. A plurality of displays 42 (six in this preferredembodiment) are mounted on an articulating arm 44 from the ceiling. Thedisplays 42 display images from the imaging system 32, and screens fromthe control system for operating the magnet units 28 and 30. A pluralityof controls 46 are provided on the patient bed 26 for operating a userinterface to control the magnet units 28 and 30, in conjunction with thescreens displayed on the displays 42.

The control room 24 includes a cabinet 48 for a processor for operatingthe user interface for controlling the magnet units 28 and 30. Aplurality of displays 50 (two in this preferred embodiment) are providedfor displaying images from the imaging system 32, and screens from theuser interface. A plurality of controls 52 are provided on the patientbed 26 for operating a user interface to control the magnet units 28 and30, in conjunction with the screens on the displays 52.

Each of the magnet units 28 and 30 projects a strong magnet field fromits front face, so that together, the magnets provide a magnet field ofsufficient strength to orient a magnetic medical device in an operatingregion in the patient on the patient bed 26. Because of the strength ofthe field projected by the magnet units 28 and 30, the units arepreferably rotatably mounted to swing between an operative position inwhich the units face the patient support, and project a field into theoperating region in the patient on the patient bed, and a stowedposition, in which the magnet units do not face the patient bed.

As shown in FIG. 2, each of the magnet units 28 and 30 comprises amagnet 100, a mechanism 200 for moving the magnet to change the magneticfield applied by the magnet 100 to the operating region in a patient,and a pedestal 700, for supporting the mechanism 200 and magnet 100. Asdescribed in more detail below the magnet 100 is preferably a compoundmagnet designed so that relatively small translations and/or rotationsresult in significant changes in the magnetic field direction projectedinto an operating region in the patient. As described in more detailbelow, the mechanism 200 is adapted to support and translate and/orrotate the magnet 100 to change the direction of the field applied bythe magnet to the operating region in the patient. The magnet 100 andthe mechanism 300 are preferably designed so that they can project amagnetic field in any direction in the operating region in the patient,or at least so that when both magnet units 28 and 30 are positioned onopposite sides of the patient, the combined effect of the magnets fromthe units projects a magnetic field in any direction.

In this preferred embodiment, the mechanism preferably provides threemovements of the magnet 100: translation of the magnet toward and awayfrom the patient (referred to herein as translation in the z-direction),rotation of the magnet about an axis parallel to the z-direction,referred to herein as rotation in the θ-direction, and pivoting of themagnet about an axis perpendicular to the θ-axis, referred to herein aspivoting in the φ direction. The movements of the magnet 100 in the zdirection, the θ-direction, and the φ direction permitted by themechanism 300 are sufficient to create a magnetic field of suitablestrength for magnetic navigation, in any direction in the operatingregion in the patient. Of course, additional or different translationsand or rotations could be provided for the same or different magnetdesign. The strength of the field projected by the magnets is preferablyat least 0.05, and more preferably at least 0.09.

The magnet 100 is preferably comprised of a plurality of block 102arranged and mounted on a backing plate 104, for example with adhesivethe magnet 100 further includes a cover 106, preferably with a smooth,contoured finished surface enclosing the assembly of blocks 102. Each ofthe blocks is made of a permeable magnetic material, and has a size,shape, position and magnetization direction to optimize field properties(direction and strength) while accommodating manufacturing. Examples ofsuitable magnets are disclosed in magnets such as those disclosed inU.S. patent application Ser. No. 10/082,715, filed Feb. 25, 2002, U.S.patent application Ser. No. 10/056,227, filed Jan. 23, 2003, and/or U.S.patent application Ser. No. 09/546,840, filed Apr. 11, 2000, thedisclosures of all of which are incorporated herein by reference.

The magnet 100 and mechanism 300 are mounted on pedestal 800. Asindicated above, and described in more detail below, the pedestal 800 ismounted for pivoting about a post 802, and has wheels 804 which allowthe pedestal to pivot from a stowed position, in which the magnet 100generally faces away from the patient, to an operative position in whichthe magnet generally faces the patient.

The magnet 100 and mechanism 300 are preferably enclosed is a cover 200to protect the mechanism from interference, to prevent persons frombeing injured or property from being damaged by the mechanism, to reducepatient anxiety, and to enhance the appearance of the unit. As shown inFIG. 3, this cover includes a frame 202 slidably mounted around the baseof the mechanism 300. As shown in FIG. 4, the cover also comprises afront base cap 204, which is generally U-shaped and adapted to besecured on the front and sides of the pedestal 800, a top base cap 206,which is adapted to be secured over the top of the pedestal, around themechanism 300, and a rear base cap 208, which is adapted to be securedon the back of the pedestal cap device. As shown in FIG. 5, the cover200 also comprises a front panel 210, adapted for mounting on the frame202 over the front of the magnet 100 and mechanism 300, and left andright side panels 212 and 214 adapted for mounting on the frame 202 overthe sides of the magnet and mechanism. An inverted U-shaped frame 216 ismounted on the frame 202 over the back of the mechanism 300. The frame216 mounts a conduit 218 for enclosing power and control leads, and aback panel 220 for covering the back of the mechanism. A cooling fanunit 222 is mounted on the frame 202, inside the panel 220 to circulateair inside the cover through louvered openings formed in the cover 220.

As shown in FIG. 8, the mechanism 300 preferably comprises a φ pivotmechanism 302, for pivoting the magnet 100 in the φ direction; aθ-rotation mechanism 402, for rotating the magnet 100 in theθ-direction; and a z-drive mechanism 602 for translating the magnet inthe z-direction.

As shown in FIGS. 15–22, the φ pivot mechanism 302 comprises a frontplate 304, adapted for mounting the magnet 100. The front plate 304 ispivotally mounted to a back plate 306. The back plate 306 is adapted tobe mounted on the θ-rotation mechanism 402, and has two parallelbrackets 308 and 310 projecting from its front face for mounting thefront plate 304. A hub 312 on the back of the front plate 304 ispivotally mounted between the brackets 308 and 310, so that the frontplate can pivot. In this preferred embodiment, the front plate 304, andthus the magnet 100 mounted on the front plate can pivot plus and minus40°, for a total range of motion of 80°. This range of motion is basedupon the properties of the magnet 100, which in this preferredembodiment provides a 180° change in field direction over a range ofpivoting of 80°. With a different magnet, the range of pivoting could bemade larger or smaller, as desired.

As best shown in FIG. 23, a motor brake 314 is mounted on bracket 308, amotor mounting adapter 316 is mounted over the motor brake on thebracket 308. A motor 318 is mounted on the mounting adapter 316, to turndrive shaft 320 having key 322 thereon. A housing 24 encloses the motor318. The drive shaft 320 engages the front plate 304 so that rotation ofthe drive shaft caused by motor 318 causes the plate to pivot about theφ pivot mechanism.

A +φ limit switch 324 is mounted on a block 326 on the front face ofplate 306, and is adapted to engage a stop 328 on the front plane 304.Similarly, a −φ limit switch 330 is mounted on a block 332 on the frontface of plate 308, and is adapted to engage a stop 334 on the frontplate. A theta sensor flag 336, which is used by the theta positionsensor as described below, is secured on the back plate 306. Phi sensorflags 338 are secured on the back of front plate 304. A rotary encoder340 is mounted on an encoder mounting plate 342, on the bracket 310, andis driven by the key 322 on the drive shaft 320.

The θ rotation mechanism 402 is shown in FIGS. 24–28. The θ rotationmechanism 402 comprises a carriage 404, which is preferably made ofaluminum or other strong, lightweight, non-magnetic material. As bestshown in FIG. 28, the carriage 404 has a generally cylindrical opening406 therein in which the outer race of a bearing 408 is mounted. Frontand rear retaining hubs 410 and 412 are secured together, sandwichingthe inner race of the bearing 408 between them. A retaining ring ismounted in the carriage 404 over the front retaining hub 414. The phipivot mechanism 302 is mounted to the front retaining hub 410, forrotation around about the theta axis.

A position sensor 416 is mounted in a recess in the front of thecarriage 404, and is triggered by the flag 338 on the phi pivotmechanism.

A cam tray 420, mounting a cam 422, is also secured on the bottom of thecarriage 404. A plurality of stops 424 are also mounted on the bottom ofthe carriage 404. A pair of C-shaped brackets 426 are mounted on thebottom of the carriage for engage and moving the cover as the thetamechanism 402 moves in the z direction, as described below. A precisiongear 428 is mounted on a bracket 430 on the bottom of the carriage. Theprecision gear is used in sensing the position in the z-direction as aback up to the position sensing built in to the z drive mechanism 602.

The driver for the θ rotation mechanism 402 is indicated generally as434 in FIGS. 29–33. The driver 434 comprises a servo motor 436, a gearbox 438, a reducer mounting plate 440, and a pinion 442. The pinion 440engages and drives a gear 442 secured to the rear hub 444, causingrotation in the theta direction.

As shown in FIGS. 35–38, the z drive mechanism 602 comprises base plate604. Mounting plates 606 are provided on the underside of base plate, oneither side, for securing the base plate to the pedestal 800. Tracks 608and 610 are mounted on the plate 604. Two carriages 612 are slidablymounted on each of the tracks 608 and 610, for slidably mounting thecarriage 404 of the theta drive mechanism 402. A servo motor 614 ismounted on the base plate 604 with a bracket 616. A flexible shaftcoupling 618, drive screw bearing 620 connect ball screw shaft 622 tothe servo motor 614. The end of the ball screw shaft 622 is supported indrive screw bearing 624. A bracket 626 is mounted on the ball screwshaft 622 and is secured to the underside of the carriage 402, to movethe carriage.

Stops 628 are mounted on the base plate 604 adjacent one end. Stops 630are mounted on the base plate 604 adjacent the other end. Limit switches632 and 634 are mounted on the plate 604 with brackets 636 an 638,respectively. A rotary encoder 640 is mounted on the base plate 604, andhas a pinion 642. The pinion 642 engages the precision gear 428 on thebottom of the carriage 404, and measures the position of the carriagerelative to the base plate 604. Rails 644 are mounted on the sides ofthe base plate 604 for slidably mounting the cover 200.

As shown in FIG. 39, the pedestal 800 comprises a frame 808, with aplatform 810 for mounting the mechanism 402. The pedestal 800 ispivotally mounted for rotation about post 402, which is secured to thefloor of the operating room. A collar 812 secured to the frame 808surrounds, and rotates around the post 402. A drive mechanism 814 ismounted in the frame 808, for driving the pedestal 800 to rotate aroundthe post 402. A lock mechanism 816 is also mounted in the frame 808, forsecuring the pedestal against movement.

As shown in FIGS. 40 and 45, the post 802 is surrounded by a weldment818. A stop tube 820 is mounted over the post 802, providing stops 822and 824 for limiting the rotational movement of the pedestal. Lowerouter mounting plate 826 and lower inner mounting plate 828, and upperouter mounting plate 830 and upper inner mounting 832 are secured aboveand below block 834, mounting spherical bearing 836. Limit switches 838,840, 842, and 844 are mounted on the upper mounting ring and are trippedby movement relative to cam 846 secured on the top of the post 802.

As shown in FIGS. 40 and 46, the drive mechanism 814 comprises a motor848 connected to gear box 850. A hand crank 852 on shaft 854 is alsoconnected to gear box 850. Sheaves 856 and 858 and belt 860 connect thegear box 850 to the drives shaft 862, which in turn drives drive wheel864. Thus the motor can operate the drive wheel, or in a situation wherepower is not available, hand crank 852 an be used to operate the drivewheel, and pivot the pedestal around post 802.

As shown in FIGS. 40 and 47, the lock mechanism 816 comprises anelectric motor 870 which turns a gear box 872 to pull or push rod 874.The pulling or pushing of the rod 874 causes the lock member 876 topivot. The lock member 876 has a tab 878, which pivots into and engagesa slot in the floor of the procedure room. A hand crank 880 on shaft 882also turns the gear box 872, to manually pull or push rod 874. An springbiased interlock bar 884, interferes with the hand crank, and must bemanipulated out of the way in order to manually operate the lockmechanism 816.

1. A magnet system for applying a magnetic field of selected directionto an operating region inside a patient on a support, to control amagnetic medical object in the operating region, the magnet systemcomprising first and second magnet applicators on opposite sides of thepatient support, each magnet applicator comprising a base, and a magnetmounted on the base, each base being movable to change the positionand/or orientation of the magnet relative to the operating position, tomove the magnet from a state in which magnet applies a field to theoperating region, and a second position in which the magnet does notapply a field to the operating region.
 2. The system according to claim1 wherein the bases pivot to change the orientation of the magnetrelative to the patient.
 3. The system according to claim 1 wherein thebases pivot to change the position and orientation of the magnetrelative to the patient.